This invention relates to a liquid meter for measuring a total amount of a liquid flowing through a path therefor. It should be noted here that this invention is applicable to a meter for measuring an amount of a liquid although a water meter is described throughout the instant specification.
A conventional water meter comprises an impeller or a turbine wheel in a path of water connected to a conduit or pipe for the water and several conversion or reduction gear trains for transmitting rotation of the impeller to a plurality of pointers or hands of an indicator to make them indicate the amount of the water used. Such conventional water meters have long been used and are featured by the simple structure. The conventional water meter, however, is defective in that a weak current or flow can not be measured because the torque given thereby is insufficient to drive the gears. Several attempts have been made to reduce the driving torque to a minimum. The torque, however, can not be reduced beyond a certain limit insofar as gears are used.
A water meter is known to Applicants which comprises no mechanical gears to remove the above-mentioned defects. More specifically, an electronic circuit is substituted in the known water meter for the gear trains in the sophisticated meter. The known water meter is suitable when the impeller rotates in proportion to an actual amount of water used but fails to indicate a correct amount when the rotation of the impeller is not accurately proportional to the actual amount of the water. This occurs when the weak current flows through the path, as will later be described with reference to one figure of the accompanying drawing. Thus a detection error takes place in the known water meter.